JP5552308B2 - Production apparatus and production method for thermoplastic resin particles - Google Patents

Description

  The present invention relates to a manufacturing apparatus and a manufacturing method for manufacturing thermoplastic resin particles by an underwater hot cut method.

  As a method for producing thermoplastic resin particles, the resin is extruded in a molten state from a die nozzle, cooled and solidified by cooling water or cooling air, and the cooled resin is cut into particles by rotating a cutting blade. The hot cut methods of the prior arts 1 and 2 have been proposed (see, for example, Patent Documents 1 and 2).

In the prior art 1, by using a pelletizer having a cutting blade made of a high hardness alloy having a Rockwell hardness HRA of 89 or more and a bending strength of 180 kgf / mm ² or more, a high hardness inorganic filler and It is said that even a resin composition containing a synthetic resin can be stably pelletized without impairing the wear resistance.

In the prior art 2, by using a die having a thermally insulated surface, the molten resin fed into the die hole from the extruder is extruded into water and cut with a rotary cutter, so that a small particle size of 0.8 to 2.0 mm and It is said that spherical particles with high sphericity can be produced, and damage to the blade and the die can be prevented by making the blade of the rotary cutter non-contact with the die surface.
Such small-sized resin particles (so-called “micropellets”) are impregnated with a foaming agent and used to produce foamed resin particles.

JP-A-11-77671 JP-A-5-301218

  In the case of the prior art 1, since the cutting blade made of a high hardness alloy is used, there is a problem that the die surface is easily worn and the life of the die is shortened, and the cutting blade and the die surface are caused by scratches generated on the die surface. As a result, a fine gap is formed between them and the cutting accuracy is lowered, and as a result, there is a problem in which connected particles C in which two or more string-like foreign substances, resin powder, and pellets p as shown in FIG. is there.

In the case of the prior art 2, when pelletizing resin that is difficult to cut (for example, olefin resin), cutting failure occurs if the blade of the rotary cutter is not in contact with the die surface.
Further, in the prior art 2 which is an underwater hot-cut method, when a micropellet having a small diameter (especially 1.5 mm or less) is obtained by cutting the rotary cutter blade in contact with the die surface, the rotational speed of the rotary cutter is reduced. Since it is set quickly, the current value required for rotation also increases. At this time, if the contact area between the blade and the die is large, these frictional resistances are also increased, so that the load on the motor for rotating the rotary cutter becomes higher and the life of the pelletizer is shortened.

  The present invention has been made in view of the above-described problems, and can suppress the generation of defective particles due to defective cutting, and reduce the frictional resistance between the cutting blade and the nozzle die surface to extend the life of the pelletizer. It is an object of the present invention to provide a production apparatus and production method for thermoplastic resin particles capable of producing a thermoplastic resin particle.

Thus, according to the present invention, the surface of the nozzle die has a nozzle die having a nozzle formed on the surface thereof, the extruder for extruding the molten thermoplastic resin from the nozzle, and the cooling water for cooling the resin extruded from the nozzle. A cooling chamber portion provided on the side, and a cutting blade provided in the cooling chamber portion and having a blade portion for cutting the resin cooled by being extruded from the nozzle by rotating while contacting the surface of the nozzle die, A rotation drive unit that rotates the cutting blade, and a cooling water circulation system that supplies cooling water into the cooling chamber and discharges it together with the resin particles to circulate only the cooling water in the cooling chamber.
Cutting blade, the thickness of the blade portion is t, the diameter of the nozzle when the d, meets the relationship 1 ≦ t / d ≦ 17,
The cutting blade has a thickness t of the blade portion of 0.5 to 5.0 mm,
An apparatus for producing thermoplastic resin particles for producing thermoplastic resin particles having a particle diameter of 0.3 to 1.5 mm is provided.

  Further, according to another aspect of the present invention, the molten thermoplastic resin is extruded from the nozzle die of the extruder in the manufacturing apparatus, cooled with cooling water in the cooling chamber, and the cutting blade is rotated. A method for producing thermoplastic resin particles for cutting a cooled resin into particles, and thermoplastic resin particles produced by the production method are provided.

According to the present invention, it is possible to suppress the generation of defective particles due to defective cutting and the generation of pellets having a bite, and it is possible to extend the life of the pelletizer by reducing the frictional resistance between the cutting blade and the nozzle die surface.
In addition, micropellets having a particle size of 0.3 to 1.5 mm can be manufactured while keeping the generation rate of defective particles and foreign matters low.
In the present invention, pellets (resin particles) are not spherical because they are formed by cutting columnar resin from the nozzle. Therefore, in the present specification, the “particle diameter” of the pellet means an average value of dimensions of (major axis L + minor axis D) / 2 with respect to the cross section of the pellet of ten samples.

FIG. 1 is a block diagram showing an embodiment of an apparatus for producing thermoplastic resin particles according to the present invention. 2 is a side sectional view showing a schematic configuration of a nozzle die in the manufacturing apparatus of FIG. FIG. 3 is a front view showing a nozzle die in the manufacturing apparatus of FIG. 4A and 4B are cross-sectional views showing a contact portion between the cutting blade and the nozzle die surface in the manufacturing apparatus of the embodiment. 5A and 5B are cross-sectional views illustrating a state in which the resin is cut with the cutting blade of FIG. It is a conceptual diagram which shows the connection particle | grains which two or more pellets connected.

An apparatus for producing thermoplastic resin particles according to the present invention includes an extruder having a nozzle die having a nozzle formed on the surface thereof, and an extruder for extruding a molten thermoplastic resin from the nozzle, and cooling water for cooling the resin extruded from the nozzle. A cooling chamber portion provided on the surface side of the nozzle die, and a blade portion provided in the cooling chamber portion for cutting the resin cooled by being extruded from the nozzle by rotating while contacting the surface of the nozzle die. And a rotation drive unit that rotates the cutting blade, and a cooling water circulation system that supplies cooling water into the cooling chamber and discharges it together with the resin particles to circulate only the cooling water in the cooling chamber.
In the present specification, the term “resin” simply means “thermoplastic resin” unless otherwise specified.

This thermoplastic resin particle production apparatus (hereinafter referred to as “resin particle production apparatus”) is an underwater hot-cut resin particle production apparatus, which is a main part for cutting resin extruded from a nozzle into particles. focusing on a certain cutting blade and nozzle die, cutting blade, the thickness of the blade portion is t, when the diameter of the nozzle is d, meets the relationship 1 ≦ t / d ≦ 17, the cutting blade, the blade portion The thermoplastic resin particles having a thickness t of 0.5 to 5.0 mm and a particle diameter of 0.3 to 1.5 mm are manufactured, thereby solving the problems of the prior arts 1 and 2. be able to.

When the ratio t / d is larger than 17, the contact area between the blade portion of the cutting blade and the nozzle die surface becomes too large, and therefore the cutting blade is rotated at the same rotational speed as compared with the case where the contact area is small. The load on the rotation drive unit (particularly, a power source such as a motor) increases, and the life of the rotation drive unit is shortened. The blade portion of the cutting blade has a thickness at the tip portion that contacts the nozzle die surface, and even if the thickness is small, the thickness gradually increases due to friction with the nozzle die surface, so the ratio t / d is 1 or more. Although the ratio t / d is sufficient if 17 or less.

This resin particle manufacturing apparatus may be further configured as in the following (1) and (2), or a combination thereof.
( 1 ) As for the cutting blade, the material of the blade portion has a hardness of Rockwell hardness HRC of 50 to 70, and the material of the surface of the nozzle die has a hardness of Rockwell hardness HRC of 55 or more.
In this case, examples of the material for the surfaces of the cutting blade and the nozzle die include WC-Co, TiN-Ni, and TiC-Ni alloys.
In addition, since the nozzle die is more expensive than the cutting blade, it is preferable that the hardness of the nozzle die surface is harder than the hardness of the blade portion of the cutting blade, but if the hardness is within the above range, the problem is Absent.

( 2 ) The rotation drive unit includes a motor, a rotation shaft that is rotated by the motor, and a cutting blade holder provided at a tip of the rotation shaft in the cooling chamber, and the cutting blade is a rotation shaft of the cutting blade holder. A plurality of nozzles are provided at equal intervals in the circumferential direction around the center, and a plurality of nozzles are provided in the circumferential direction around the rotational axis.
In this way, it is possible to deal with mass production.

The method for producing thermoplastic resin particles of the present invention includes extruding molten thermoplastic resin from a nozzle die of an extruder in the resin particle production apparatus having the above-described configuration, cooling it with cooling water in a cooling chamber, and cutting. It can be carried out by rotating the blade and cutting the cooled resin into particles.
In this resin particle production method, the kind of thermoplastic resin is not limited, and polystyrene resin, polyethylene resin, polypropylene resin, polyester resin, polyvinyl chloride resin, ABS resin, AS resin, etc., alone or in two kinds The above may be sufficient and the collection | recovery resin once used may be sufficient. In particular, a particle size of 0.3 to 1 made of a thermoplastic resin that has an elongation of 100 to 3000 m / min and is difficult to cut, for example, a resin such as linear low density polyethylene (LLDPE) or polypropylene (PP). It is suitable for producing resin particles (micropellets) of 5 mm. Moreover, it is good also as a foaming resin particle by making a thermoplastic resin contain a foaming agent within an extruder.
In this case, the peripheral speed of the cutting blade is suitably 4 to 70 m / s. In addition, when the peripheral speed of a cutting blade is slower than 4 m / s, it will become easy to generate | occur | produce a cutting defect, and since it will become an overload when it exceeds 70 m / s, it is unpreferable.

Here, the breaking speed is a value measured under the following conditions.
Measuring device: Twin pore capillary rheometer (Rheologic 5000T (Chiast, Italy))
Test temperature: 210 ℃
Capillary shape: A Barrel diameter 15mm, Die diameter 1mm, Die length 10mm,
Inflow angle 90 degrees (conical)
Extrusion speed: 0.0773mm / s (Q = 0.75g / min)
Cutting speed: Accelerated at an initial speed of 17.4 mm / s to 12 mm / s ² Note that in the present invention, micro pellets with reduced defective particles such as connected particles are produced from the above-mentioned thermoplastic resin that is difficult to cut. Therefore, if the resin is easier to cut than the elongation rate in this range, it is possible to produce a micropellet with further reduced defective particles.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing an embodiment of a thermoplastic resin particle manufacturing apparatus according to the present invention, FIG. 2 is a side sectional view showing a schematic configuration of a nozzle die in the manufacturing apparatus of FIG. 1, and FIG. It is a front view which shows the nozzle die in the manufacturing apparatus of 1, and FIG. 4 (A) and (B) are sectional drawings which show the contact part of the cutting blade and nozzle die surface in the manufacturing apparatus of embodiment, FIG. And (B) are cross-sectional views illustrating a state in which the resin is cut with the cutting blade of FIG.

As shown in FIGS. 1 and 2, the thermoplastic resin particle production apparatus is a granulation apparatus T that performs granulation by an underwater hot cut method, and has a nozzle die 1 on the front end side and a hopper 21 on the rear end side. An extruder 2 having the above, a chamber (cooling chamber part) 4 for cooling the resin extruded from the nozzle 15 of the nozzle die 1 to the resin discharge surface 13, and a resin contained in the chamber 4 and extruded to the resin discharge surface 13 A cooling water circulation system having a cutter 3 having a cutting blade 30 for cutting into particles, a rotation driving unit (not shown) for rotating the cutter 3, a pipe 5 for circulating cooling water in the chamber 4, and a water supply pump 6. With.
In the granulating apparatus T and the nozzle die 1 (hereinafter referred to as “granulation die 1”), the side from which the resin is discharged is referred to as “front end” or “front side”, and the opposite side is referred to as “rear end” or “rear side”. As described.

  The chamber 4 is connected to the pipe 5 for flowing cooling water (circulated water), and one end (upstream side of the chamber 4) of the pipe 5 is connected to the water tank 7 through the water pump 6. Yes. The other end (downstream side of the chamber 4) of the pipe 5 is provided with a dehydration processing unit 8 for separating the thermoplastic resin particles from the cooling water and dehydrating and drying them. The thermoplastic resin particles separated, dehydrated and dried by the dehydration processing unit 8 are sent to the container 9.

As shown in FIGS. 2 and 3, the granulation die 1 includes a die body 10 and a die holder 11 fixed to the distal end side of the extruder 2, and the die body 10 includes a plurality of die bodies 11 on the distal end side of the die holder 11. It is fixed by bolts 12.
The die holder 11 is provided so as to be connected to the cylinder of the extruder 2, and a rear end side flow path 11a and a front end side flow path 11b are formed in that order from the rear end side toward the front end side.
The die main body 10 is formed with a conical convex portion 10a that protrudes rearward at the central portion of the rear end surface, and the die main body 10 and the die holder 11 are connected to each other with the tip-side flow path of the die holder 11 therebetween. A conical convex portion 10a is inserted into 11b with a predetermined gap.
That is, the resin that has passed through the rear end side flow passage 11a of the die holder 11 flows along the peripheral surface of the conical convex portion 10a in the front end side flow passage 11b, and a plurality of resin flow passages open to the rear end face of the die body 10. 14 (described later).

The die body 10 includes a resin discharge surface 13 that is in contact with the water flow at the front end surface thereof, a plurality of resin flow paths 14 for transferring the resin extruded from the extruder 2 toward the resin discharge surface 13, and a plurality of resin flow paths 14. A plurality of nozzles 15 that are provided at the tip of the resin flow path 14 and open to the resin discharge surface 13, and the resin discharge surface 13, the resin flow path 14, and the die body at a position closer to the extruder 2 than the resin discharge surface 13. And a heater 18 for heating 10 is schematically configured.
The heater 18 can be appropriately selected and used from conventionally known cartridge heaters according to the size and shape of the die body 10. That is, as the heater 18, for example, a heating wire (nichrome wire) wound around a rod-shaped ceramic is inserted into a pipe (heat resistant stainless steel), and the gap between the heating wire and the pipe is excellent in high thermal conductivity and high insulation. It is possible to use a bar heater with a high power density, which is encapsulated with a new material (MgO).

The resin flow path 14 extends in a direction orthogonal to the resin discharge surface 13 and has a circumference (circumference drawn on the resin discharge surface 13) around the central axis P of the die body 10. It is arranged at regular intervals along.
The nozzles 15 are arranged at a predetermined interval along the circumference drawn on the resin discharge surface 13. More specifically, the nozzle 15 is a nozzle unit in which a plurality of single nozzles 15a, 15b, 15c,... Are arbitrarily arranged within the range of the cross-sectional shape of the resin flow path 14 (in the present invention, this is referred to as “ Called a "nozzle").
As the arrangement method of each single nozzle 15a, 15b, 15c,..., For example, a method in which a large number of small nozzles are arranged on a plurality of small circles can be adopted. However, the arrangement method is limited to such an arrangement form. The cross-sectional shape of the hole is not limited to a circle, and may be an ellipse or a rectangle.
Hole diameter d of the nozzle 15, as possible out be appropriately set according to the size of the micropellets to be finally obtained.

The cutter 3 includes a holder having a rotation axis at the rotation center, and the plurality of cutting blades 30 attached to the holder at regular intervals in the circumferential direction.
The rotating shaft is disposed on an axis line that coincides with the central axis P of the die body 10, one end of which is connected to the holder, and the other end is inserted in a liquid-tight hole in the chamber 4 and protrudes to the outside. Yes.
The number of cutting blades 30 is not particularly limited, and can be the same as the number of nozzle units, for example.
The shape of the blade portion 30a of the cutting blade 30 is not particularly limited, and the ratio t / d between the thickness t of the contact portion of the blade portion 30a with the resin discharge surface 13 and the diameter d of the nozzle 15 is 1 ≦ t / d. ≦ 17 may be satisfied, for example, a shape having a certain thickness as shown in FIG. 4 (A) or a shape that becomes thinner toward the contact portion as shown in FIG. 4 (B). Can do.
Therefore, the thickness t of the blade section 30a, d is not good satisfies the relationship of 1 ≦ t / d ≦ 17.

A rotation drive unit (not shown) is provided outside the chamber 4 and is connected to the rotation shaft of the cutter 3.
Further, a support mechanism (not shown) is provided outside the chamber 4. The support mechanism can move the cutter 3 and the rotation drive unit in the direction of the rotation axis, and the cutting blade 30 is a resin discharge surface of the die body 10. It is comprised so that it can support in the state pressed against 13 by predetermined pressure. In addition, the pressure at the time of pressing the cutting blade 30 against the resin discharge surface 13 of the die body 10 is not particularly limited, but for example, about 0 to 2 bar is appropriate, and usually 0.5 to 1.0 bar. It is.

According to the resin particle manufacturing apparatus configured as described above, for example, as shown in FIG. 5 (A), the cutting blade 30 moves toward the resin R that has come out of the nozzle 15 into the cooling water W. As shown in FIG. 5B, the resin particle r can be produced by cutting the resin R with the blade portion 30a.
Even after cutting, the resin R coming out of the nozzle 15 is cut by the next cutting blade 30 and this cutting process is repeated to produce a large amount of resin particles r.

500 kg of the resin particles of Examples 1 to 5 and Comparative Examples 1 to 2 were produced under the conditions shown in Table 1 using the resin particle production apparatus described with reference to FIGS.
At this time, in Examples 1-5 and Comparative Examples 1-2, the Rockwell hardness HRC of the blade portion of the cutting blade is 58, the Rockwell hardness HRC of the nozzle die surface is 60, and the nozzle die surface of the cutting blade The pressing pressure on was 0.5 bar.
In addition, the pelletizer current values, the particle diameters of the resin particles, the number of connected particles and their pass / fail, the pellet shape, and the number of pellets having a puddle in each example and each comparative example were examined, and the results are shown in Table 1.

The pelletizer current value is a current value necessary for driving the motor of the rotational drive unit, and is preferably 10 A or less.
The number of connected particles (%) is a value by which the defect rate can be judged, and was calculated by the following formula.
Number of connected particles (%) = [number of connected particles / (10 g × 100 grains / weight of 100 pellets) (g)] × 100
The pellet shape was indicated as “good” in the form of particles.
The acceptance / rejection determination of the pellet is indicated by “◎” as a pass (excellent) when the number of connected particles is less than 0.2%, and indicated by “◯” as a pass (good) when less than 0.2 to 2%. 2% or more was shown as “x” as rejected.
The number of pellets having a beat is the ratio (%) of the number of pellets having a beat when 100 manufactured pellets are extracted.
Here, “sasare” means a rod-like material at the pellet cutting position, which is generated when the resin coming out of the nozzle is cut by a cutting blade, and has a length of 10% or more of the pellet diameter. It is defined as

In Examples 2 to 5 where the ratio t / d between the thickness t of the blade contact portion of the cutting blade and the diameter d of the nozzle satisfies the relationship of 1 ≦ t / d ≦ 17, the number of connected particles is less than 2%, and it is easy Resin particles can be produced with the pellets having a content of less than 20%, and the pelletizer current value can also be suppressed to 10.0 A or less.
On the other hand, in Comparative Example 1 in which the cutting blade and the resin discharge surface of the die body were not in contact, the resin discharged from the nozzle was wound around the cutting blade and could not be cut into a pellet shape.
Further, in Comparative Example 2 in which the ratio t / d exceeds 17, the number of connected particles was 2% or more and the number of pellets having a whirl increased to 35%, and thus all were inappropriate for the production of resin particles.

1 Nozzle die (granulation die)
2 Extruder 3 Cutter 4 Chamber (cooling chamber)
5 Pipe line 6 Water pump 7 Water tank 8 Dehydration section 8
DESCRIPTION OF SYMBOLS 9 Container 10 Die body 10a Conical convex part 11 Die holder 11a Rear end side flow path 11b Front end side flow path 13 Resin discharge surface 14 Resin flow path 15 Nozzle 15a, 15b, 15c, ... Single nozzle 30 Cutting blade 30a Blade part d Nozzle diameter P Center axis R Resin r Resin particles T Granulator t Thickness of contact portion of blade portion with resin discharge surface W Cooling water

Claims (8)

An extruder having a nozzle die having a nozzle formed on the surface thereof and an extruder for extruding a molten thermoplastic resin from the nozzle, and a cooling chamber provided on the surface side of the nozzle die so as to accommodate cooling water for cooling the resin extruded from the nozzle A cutting blade having a blade portion that is provided in the cooling chamber portion and rotates while contacting the surface of the nozzle die to cut the resin cooled by being extruded from the nozzle, and a rotational drive that rotates the cutting blade A cooling water circulation system for supplying cooling water into the cooling chamber and discharging it together with the resin particles to circulate only the cooling water in the cooling chamber,
Cutting blade, the thickness of the blade portion is t, the diameter of the nozzle when the d, meets the relationship 1 ≦ t / d ≦ 17,
The cutting blade has a thickness t of the blade portion of 0.5 to 5.0 mm,
An apparatus for producing thermoplastic resin particles, comprising producing thermoplastic resin particles having a particle diameter of 0.3 to 1.5 mm . Cutting blade, the blade section of the material has a hardness of Rockwell hardness HRC 50 to 70, the material of the surface of the nozzle die according to claim 1, Rockwell hardness HRC has a hardness of 55 or more Equipment for producing thermoplastic resin particles. The rotation drive unit has a motor, a rotation shaft that rotates by the motor, and a cutting blade holder provided at the tip of the rotation shaft in the cooling chamber,
A plurality of cutting blades are provided at equal intervals in the circumferential direction around the rotation axis of the cutting blade holder,
The nozzle apparatus for producing a thermoplastic resin particle according to claim 1 or 2, a plurality provided in a circumferential direction about said rotation axis. According cooled in claim 1-3 for any one thermoplastic resin extruded cooling chamber portion of the cooling water that has melted from the nozzle of the nozzle die in the manufacturing apparatus described, and cooled cutting blade is rotated resin A method for producing thermoplastic resin particles by cutting particles into particles. The method for producing thermoplastic resin particles according to claim 4 , wherein the peripheral speed during rotation of the cutting blade is set to 4 to 70 m / s. The method for producing thermoplastic resin particles according to claim 4 or 5 , wherein the thermoplastic resin has an elongation at a breaking point speed of 100 to 3000 m / min. The method for producing thermoplastic resin particles according to any one of claims 4 to 6 , wherein the thermoplastic resin is linear low-density polyethylene or polypropylene. The thermoplastic resin particle manufactured by the manufacturing method of the thermoplastic resin particle as described in any one of Claims 4-7 .